Polycarbonate (PC) and blends of polycarbonate with acrylonitrile, butadiene, and styrene terpolymer (PC/ABS) have found many uses in general, and specifically in medical devices, because polycarbonate combines a high level of heat resistance, transparency, good impact resistance, and it is easily molded. However, the prevalence of hospital acquired infections (HAI) requires medical devices to be exposed to a variety of commonly used cleaning liquids and polycarbonate, even blended with ABS, can suffer from a tendency to craze and crack under the effects of residual molded-in stresses, especially when contacted with such cleaning solutions. Polycarbonate which has crazed is, undesirably, more likely to experience brittle rather than ductile failure. This disadvantage has been somewhat relieved by the practice of blending polycarbonate with various substances such as the olefin polymers polyethylene, polypropylene, polyisobutylene, polyphenyleneoxide, or polyester as described for example in U.S. Pat. Nos. 3,431,224; 5,189,091; 5,262,476; 5,369,154; and 5,461,092. These added substances are capable of improving the resistance of polycarbonate to solvents, but they tend to cause an offsetting reduction in impact resistance and weldline strength of the blended composition. Additionally, it is frequently found that when the polycarbonate is modified with substances such as polyolefins, the added substances tend to separate in the blend from the polycarbonate and delaminate as evidenced by peeling or splintering. Commonly owned patent application PCT/EP 2011/002048 titled CARBONATE BLEND COMPOSITION HAVING IMPROVED RESISTANCE TO ENVIRONMENTAL STRESS CRACKING describes a polycarbonate blend having the purpose of improving the environmental stress crack resistance (ESCR) thereof (e.g. chemical resistance) which also does not deleteriously affect its impact strength and weldline strength, and cause delamination as evidenced by peeling or splintering.
Many articles that are prepared from polycarbonate based blends are required to exhibit fire retardant properties. Many known fire retardant compounds commonly utilized in polycarbonate blends degrade other desirable properties of such blends such as chemical resistance (resistance to environmental stress cracking), impact properties and heat resistance. What are needed are polycarbonate blends with good fire retardant properties, good chemical resistance (resistance to environmental stress cracking), impact properties and heat resistance.